Scientific Detail and Juror Decision-Making in Capital Scenarios

By providing vignettes with manipulated scientific evidence, this research examined if including more or less scientific detail affected decision-making in regards to the death penalty. Participants were randomly assigned one of the two manipulations (less science and more science) after reading a short scenario introducing the mock capital trial and their role as jury members. Survey respondents were told that a jury had previously found the defendant guilty and they would now deliberate the appropriate punishment. Before being exposed to the manipulation, respondents answered questions pertaining to their prior belief in the death penalty, as well as their level of support of procedural justice and science. These questions provided a baseline to compare to their sentencing decision. Participants were then asked what sentence they would impose \u2014 life in prison or death \u2014 and how the fMRI evidence presented by an expert witness for the defense affected their decision. Both quantitative and qualitative measures were used to identify how the level of scientific detail affected their decision. Our intended predictor variable (level of scientific detail) did not affect juror decision-making. In fact, the qualitative results revealed a variety of interpretations of the scientific evidence used both in favor of death and in favor of life. When looking at what did predict juror decision-making, gender, prior belief in the death penalty, and political ideology all were significant predictors. As in previous literature, the fMRI evidence in our study had mixed results with regards to implementation of the death penalty. This held true in both of our manipulations, showing that despite the level of detail in evidence intended for mitigation, jurors with preconceived notions may still disregard the evidence, and some jurors may even view it is aggravating and thus increase the likelihood of a death sentence for a defendant with such brain abnormalities.